Basilica, in the ancient architecture, a kind of public hall or court of judicature, where the princes or magistrates sat to administer justice. This word is taken from the Greek βασιλεῖον, a royal house, or palace.

The basilica consisted of a great hall, with aisles, porticoes, tribunes, and tribunals. The bankers, too, had one part of the basilica allotted for their residence; and scholars likewise went thither to pronounce their declamations. In after times the denomination of basilica was also given to other buildings of public use, as town-houses, exchanges, and the like. The Roman basilice were covered, by which they were distinguished from the fora, which were public places in the open air. The first basilica at Rome was built by Cato the elder, whence it was called Porcia; the second was called Opinia; the third was that of Paulus, built at great expense, and with much magnificence, whence it was called by some regia Pauli; and Julius Caesar erected a fourth called basilica Julia, of which Vitruvius tells us he had the direction. Besides these there were others, to the number of eighteen or twenty. The basilica Julia not only served for the hearing of causes, but likewise for the reception and audience of foreign ambassadors. It was supported by a hundred marble pillars in four rows, and enriched with decorations of gold and precious stones; and in it were thirteen tribunals or judgment-seats, where the praetors sat for the despatch of judicial business.